Method of making electron discharge devices



Feb. 4, 1947. F. H. MclNTOSH METHOD OF MAKING ELECTRON DISCHARGE DEVICES 4 Sheets- Sheet 1 Filed Oct. 22, 1943 Feb. 4, 1947. F. H. MOINTOISH 2,415,360

' METHOD OF MAKING ELECTRON DISCHARGE DEVICES Filed Oct. 22, 1943 4 Sheets-Sheet 2 gwua/wtom fimlllfcbrios/Z v @JQw/dmw 4 Feb. 4, 1947;

F. H. MlNTOSH METEOD OF MAKING ELECTRON DISCHARGE DEVICES 4 Sheets-Sheet 3 Filed Oct. 22,v 194s 3 rwwwtw lmlzmmm Feb. 4, 1947. F. H. McINTOSH 2,415,360

1 METHOD OF MAKIi IG ELECTRON DISCHARGE DEVICES Filed Oct. 22, 1943 assembly line production with Patented Feb. 4, 1941 UNITED STATES PATENT, OFFICE METHOD OF MAKING ELECTRON DISCHARGE DEVICES Frank H. McIntosh, Chevy Chase, Md.

Application October 22, 1943, Serial No. 507,314

. 9 Claims. 1 This invention relates to electron discharge devices and methods of making the same. More particularly, it relates to products adapted for a minimum of hand operations.

In the manufacture of electron discharge tubes of theprior art, it has been customary to make up individual units of the tubes, such as the oathode with heater, the grid and the other elements, and then to assemble them on a base to which an envelope was subsequently applied, sealed off, and evacuated. As the art has developed, the size of the tubes for ordinary amplification and detection has steadily decreased until, at the present time, some ofthe tubes are so small that hand assembly is highly impractical. Where the spacing of electrodes is critical, and it becomes more so in these very small tubes, hand methods of assembly are-not only expensive, but very wasteful and rejections sometimes run as high as ninety per cent. The whole tendency of development has, therefore, been to accentuate the production difiiculties and expenses so characteristic of hand assembly.

The present invention consists primarily in producing a structure in which the elements are all'suitably arranged to permit automatic machine or jig assembly. The electrodes may be made of sheet or wire stock and passed through the machine to be cut off after being placed in position. In this way, nothing except possibly the heaters for the cathodes will require individual assembly. It, therefore, becomes possible to make up tubes by machine on an assembly line basis, with their characteristics substantially fixed and unvarying. The number of rejects will be enormously reduced, and the replacement of damaged parts very readily provided for. Among v the objects of this invention may be mentioned the production of an electron discharge tube capable of machine assembly, possessing precision fixed spacing of the elements, mechanical stability, long life, substantial freedom from microphonic noise, and ready adaptation to particular specialized problems. An important feature of the process. is that it permits changes and Valiations in the product by simple machine adjustment, without change in the basic process or mechanism for performing it.

Other advantages will appear from the following description when read in conjunction with the accompanying drawings, in whicha Figure 1 is a perspective view of an electron discharge tube embodying the present invention,

" elements of the tubes are arranged to provide an unobstructed path for the.electron emission;

Figure 4 is a modification in whichmeans is provided for increasing the leakage path between electrodes in the assembled tube;

Figure 5 is'a view showing a modified scheme for clamping the insulating and control elements together;

Figure 6 is a view showing another method of increasing the leakage path between tube elements, and a method of effectively placing the control grid close to the cathode;

Figure 7 is a perspective. view of the interior structure of an electron discharge tube of modified form, the envelope and base being removed;

Figure 8 is a horizontal sectional view substantially on the line 8-8 of Figure '7;

Figure 9 is a diagrammatic view of one form of apparatus suitable for carrying out methods embodying the present invention;

Figure 10 is a detailed view of the mechanism for varying the spacing of the grid wires as they are fed to the machine of Figure 9;

Figure 11 is a detail view of a base to which are attached both terminals and prongs, this base being suitable for hopper feeding in the apparatus of Figure 9; and

Figure 12 is a perspective view showing the structure of Figure 1 with'certain of the gridv wires laid parallel to the axis of the cathode to minimize tube capacity.

, Referringfirst to Figure 1 of the drawings, reference character 15 designates an envelope of conventional type, capable of construction by any improved practice found in the art. it designates a base, to which the envelope: I5 is sealed, the :base being of any suitable insulating material. Mounted within the envelope is an assembly composed of a plurality of frame elements ll, which may be of any suitable insulating material, these elements being assembled as indicated,

, withelectrodes and terminal leads placed beassembly in the unit.

.ative. i After the clamps l8 are secured in position and to Figure 2, in which the exploded view indicates the position of the various parts prior to their As here indicated, the frame elements I! are square in cross section, but it is obvious that in practice they may assume various forms. For example, they may be circular in form. The unit may. be embodied in any suitable'type of structure without'reg'ardto the number of elements used. For example, it may be a triode. However, since the problem of clearances becomes increasingly acute as the number of control elements is increased,.and [since the problem appears in an accentuated fo'rmin the pentode, a pentode has been here illustrated,

In Figure 2, reference character [9 indicates the usual plate, which is disposed at the most remote position from the cathode 2! with its heater 22. Reference character 23 designates the control grid having a terminal connection 24. 25 is the high voltage or screen, grid, having a terminal plate 26, and 21 is the cathode or suppressor grid having a terminal plate 28; As indicated, these parts shown in Figure 2 are assembled in abutting relation and secured together by the clamps i8 (Fig. 1), thus holding the parts in properly spaced relation for efficient operation, the spacing being predetermined by the thickness of the various frame elements l1. When securely clamped together, these frame elements hold the parts in fixed position, with all of the electrodes under tension. This not only insures good electrical contact, but maintenance of proper contact and of proper tension in the various elements throughout the life of the tube. Another advantage of this structure is that if'any of the elements should fail; if, for example, the heater 22 should be burned out, it would be possible to dismantle the assembly, replace the burned-out heater element and reassemble the parts, without altering the characteristics of the tube and without wasting any of the parts which make up the assembly. It would be necessary merely to replace thejenvelope, seal it and evacuate the tube in the case of a tube of the vacuum type.

If the structure should be a tube of the gas-filled filling of gas in order to make the structure opertheassembled unit placed on the base [6, the en velope i5 may be placed, evacuated or filled with gas, and then sealed off. I

In Figure 1, the various terminals carried by the base [6 are indicated generally by the reference character 29. Each of these terminals is secured in the base 16 and has a lead 3i contacted with its respective connector place, and is held inposition without soldering or welding, by the clamping together of the assembled unit made up of the various frame elements, together with the electrodes. tacts may be used if desired. Control electrodes fabricated in this manner are characterized by having a. single point electrical contact between each Wire and the terminal plate. Hence, the electrode wires are never short circuited and no paths are afiorded for'the flow of circulating or eddy currents. It is possible in a structure of this type to utilize the plate I9 as an end closure for the unit. When so used this plate could function readily to radiate heat and thus cool the tube.

It is indicated in Figures 1 and 2 that the cross section of the tube is rectangular or square and Obviously welded or soldered con-' that each of the frame elements I! has the same cross sectional area. Inasmuch as the electron beam from the cathode tends to diverge as it travels away from the cathode, Figure 3 indicates a scheme whereby the effect of this divergence may be utilized to increase the efficiency of the tube. In Figure 3, reference character l'l indicates a frame element similar to the frame element shown in Figures 1 and 2, the two first frame elements holding a cathode 21 with an emitting surface 32. Interposed between a second frame element l1 and a larger successive frame element 33 is the control grid 23, corresponding to that of Figure 2. Here, the next frame element is designated 34 and it cooperates with the frame element 33 in holding the screen grid 25. The next frame element 35, which is of still greater diameter than the element 34 cooperates with the frame element 34 to hold the plate 21. In this figure, the structure illustrated is a screen grid triode, and the frame elements are held together in a manner similar to that indicated in Figure 1. It will be seen that the divergence of the electron flow path is such that the major portion of the electrons emitted from the emitting surface 32 will strike the plate 21, whereas, if the frame elements 33, 34 and 35 were of the same diameter as the element [1, substantial numbers of these electrons would strike the frame elements and be deflected or absorbed instead of striking the plate directly as in the case of the structure of Figure 3. This arrangement has the additional advantage of providing a convenient means for tying the electrodes, together in a double tube structure when a complete set of electrodes is disposed on each side of the cathode.

Figure 4 illustrates a further modified structure, in which the frame element 1! has the same structure as that indicated in Figures 1 and 2, but means is provided in the form of an insulated element 28a. interposed between the plate 21 and the two frame elements l-la, and "b, to increase the leakage path between the plate 21 and the screen grid 25. By the use of an insulating member of this character, which would necessarily assume a configuration similar to that of a frame element ll, it becomes possible to decrease the spacing between the various electrodes without decreasing the leakage path between them. Figure 4 not only shows the element 28a, but it indicates how the various frame elements may be grooved as indicated at 39 to assist in holding the electrodes under tension when the frame elements are assembled and clamped together. Here the terminals 40 are round as indicated.

Figure 5 is a partial sectional view similar to that of Figure 4, but showing a modified structure whereby the clamping action between the various frame elements is increased. Here the frame elements designated 4| have curved faces 42 adjacent their points of contact with the various electrodes. This arrangement may be advan- It is indicated above that the grid electrodes are all of tensioned wire. This may be true also of the plate. The fact that the wires are assembled under tension and supported at both ends makes it unnecessary to rely upon the stiffness of the material for support. Consequently a wire of smaller gauge and, hence, of greater efiiciency may be used. While wire is the preferred material it is obviously practicable to use woven mesh, photo-etched or perforated sheet stock as electrode material, and such use is contemplated when it is expedient. Where wires are used in building up the grids, the wire spacing may be varied as desired to produce tubes having variable mu characteristics. The wire grid structure also has a marked advantage over prior art structures in that the wires are not short circuited, and hence do not cause circulating or eddy currents to flow. Where grid wires are wound about conducting posts and welded at each point of contact, as in the usual practice, numerous paths for the flow of undesirableeddy currents are formed.

In Figure 2 it is indicated that the electrode wires in adjacent electrodes are parallel, but alternate sets may be made parallel to the axis of the cathode in order to cut down the tube capacity, especially at high frequencies. For example, and as indicated in Figure 12, the wires of grid 25 might extend parallel to the indicated position of contact strip 25. In this way no wires would contact an insulating frame directly in line with similar wires of the next electrode contacting their frame. The position of the contact strip 26 would, of course, have to be approximately changed to make it cross the wires.

This structure is produced by placing the wires alternately vertically and horizontally, observing the relation of the wires of grid 25 to other conductors as indicated above.

The structure so far described involves a radical departure from the usual practice in making vacuum tubes. While the basic underlying idea is that of making each of the electrodes uniplanar and in placing all of the electrodes in the assembled structure under tension and in parallel spaced relation so as to permit continuous or jig assembly, this arrangement involves the use of specially-constructed parts such as the frame elements. It is possible, however, to make use of stock materials of types which are available according to present practice, and to assemble them by machine, so as to accomplish many of the advantages of the present invention and to eliminate the disadvantages of prior art structures. A completed tube unit, assembled in this way is indicated in perspective in Figure 7, Figure 8 being a horizontal section to indicate more clearly how the various elements are placed. In the structures of" Figures 1 and 2, it has been indicated that thetube employs a single set of electrodes in combination with the cathode. It is, however, possible to duplicate the structure and embody the functions of two tubes in one, using a single cathode having two emitting surfaces on opposite faces. In other words, it is possible to duplicate in Figure 2, to the left of the cathode 2|, a set of grids as indicated on the right, and a plate, so that the tube will embody a single cathode, six grids and two plates. Figures -'7 and 8 indicate how this double structure can be carried out without radical departure from present practice, but ieving substantial benefits which are charac.eristic of the improved practice contemplated according to the present invention.

Referring now to Figure '7, the reference characters 5| and 52 designate insulating plates which may be of mica or other similar material held in spaced relation by insulating or metal posts 53, 54, 55 and 56. Since this figure represents a double structure, the two mica sheets 5| and 52 are secured together by eight pairs of these insulating posts, each terminating in the mica sheets 5| and 52. ported by the posts 53. These posts when made of ceramic material, such as glass, may have the plates secured together by a slight fusion of the glass to form overhanging gripping lips. Similarly, the suppresser or space charge grids 21 are supported by the posts 54. Posts 55 support the two high voltage or screen grids 25; and posts 56 support externally the two control grids 23, and internally the cathode 2|, with the enclosed heater 22. The cathode must be mounted in an insulating sheet to insulate it from the posts 56 and thus prevent short circuit of the control grids. The relation of these parts is indicated more clearly in the horizontal section of Figure 8, and it will be seen that each of the emitting surfaces of the cathode 2| is directed against one of the two sets of grids and plates. In such a structure the two grids 23 will be electrically connected. Similarly, the two grids 25 will be electrically connected and similarly for grids 21, 21 and plates 9, Hi. This arrangement then is connected as a single pentode.

When the posts 53, 54, 55 and 56' are of metal the electrode wires may be welded to'them. Welding surfaces can be inserted between the parallel electrodes and pressure applied during the welding. The wires and posts may then be cut off. The bottom plate 5| may be attaehed to aconventional tube base and connections made substantially as in Figure 1. This welded assembly may be made in a process similar to that shortly to be described.

The two mica spacer plates 5| and 52 may be enclosed in the usual glass envelope having a base carrying prongs which are connected by leads from the various electrodes and control elements of the tube structure. It is also possible, by making the sheets 5| and 52 of glass to complete the envelope by welding a glass strip around the periphery of the assembly shown. The structure may be readily shielded by the addition of shielding plates as indicated at 56, or these may be omitted.

It will be 'seen that structurally the arrangement of Figure '7 is quite similar t t t of Figures l and 2, in that all of the elements are uniplanar, all of the planes are parallel in the finished tube, and all grid wires are under tension and supported at both ends. This eliminates all grid wire windin operations and insures uniform spacing of the parts while making it possible to adapt the arrangement to continuous assembly line construction or for assembly on a suitable jig. Figures 7 and 8 show a structure in which raw sheet and wire stock may be uti- The two plates l9 are sup-,

is punched at intervals to receive a heating element, and the heaters may be assembled in the strip so that the strip as a whole, carrying the heater elements, may be fed to the machine. This will be more clearly understood from a reference to Figure 9 of the drawings, in which reference character 6!- designates a machine bed forming a raceway between two sets of feeding belts, one of them, designated 62, being driven from one of the pulleys 63. A similar belt is disposed at the back of the machine, so that the two of them form a converging throat, terminating between two spaced parallel guide members 64, secured to the base of the machine as indicated in the drawings.

Mounted at the incoming end of the raceway are aplurality of combs 66, pivoted about horizontal pivots 61, on the-machine base. The details of this comb arrangement are shown in Figure 10, where it is indicated that the perforations 68, through which the grid wires pass. provide for maximum spacing of these wires by adjusting the position of these combs. As indicatedin dotted lines in Figure 10, the spacing can be varied to suit requirements; that is, the spacing decreases as the comb approaches a horizontal position. Suitable clamping means with calibrated spacing indicators may be provided to hold these combs in any adjusted position. For simof the drawings, except that the parts are duplicated as in Figures 7 and 8. Passing into the carry the leads already connected to the prongs as indicated in Figure 11. With the assembly thus completed as aunit, a rotating cutting or shear device indicated at 83 swings downwardly between units to sever the grid, plate and cathode strips, thus releasing a completed unit as indicated. This assembly takes place continuousthroat from suitable reels is a strip of cathode material H containing the heater elements as indicated more clearly in Figure 2 of the drawin'gs. The line of separation between the individual cathodes is indicated, but the severance is not complete. Passing outwardly from this central cathode are sets of parallel moving grid wires 12 of the control grid, 13 of the screen grid, and 14 of the suppresser or space charge grid. The plate material appears at 15.

The continuous strip material be it wire or sheet stock, may be de-gassed by heating in an inert atmosphere in accordance with known practice before it enters the machine.

Disposed above the throat of the machine is a hopper 16, through which are fed sets of frame elements 41 suflicient in each, layer to produce a double pentode as indicated. When a set of insulating elements is fed downwardly between the spaced strips of element material, the assembly passes forward continuously until it is disposed under a second hopper H, from which are fed the sets of lead wires which are adapted to be clamped into the assembly so as to insure good electrical contact between the leads and the control elements of the units. After the assembly passes the hopper", the mechanism causes the side rail 64 to be swung inwardly sufficiently to compact the frame elements and to bring them in close contact with the leads l8, whereupon ly so long as the hoppers are kept filled with material, and so long as strip material and bar stock is fed into the raceway. While the terminal members 18 are indicated as being fed in finished form from the hopper 11, it will beunderstood that they may be fed from continuous bar stock and cut oil. as soon as the assembly passes the hopper 11. It is also to be understood that suitable mechanism will be utilized foractuating the parts disclosed, but since actuating mechanism of this type iswell known in the art, it is not illustrated in the drawings. When the units are completed, they may be placed in an envelope ready for sealing oif, and will then appear as in Figure 1. While the process has been described in connection with a double pentode having an internal structure corresponding to that shown in Figures 1 and 2,'it willbe obvious that it may be adapted to the manufacutre and as-' sembly of various arrangements indicated in the drawings including the form shown in Figuresl and 8. The addition of the envelopes and the sealing oiT may obviously comprise steps in the process of Figure 9.

It will be clear fromthe foregoing description, that the present invention offers numerous ad vantages over prior art schemes. It makes it possible for the first time to assemble electron discharge devices-by a continuous process which insures uniformity of product, especially as regards spacing of the elements with respect to each other. This is important, particularly in tubes of small sizes and those having five electrodes where the clearances are critical and highly important. It will also be understood that while the invention has been described as being carried out by a continuous method of assembly, it will be possible to assemble the elements by means of jigs, upon which the various operating parts are set up. Here, again, the advantage of using raw stock will beapparent. The invention, therefore, not only olfers the advantage of high speed production with improved efiiciency and .material reduction in labor costs, but it will also result in a material saving in the number of rejects and, consequently, in a marked decrease in the cost of production for both reasons.

' The invention has been described in the form of two embodiments of the electron discharge device and a single method of assembly, but it will be understood that the invention is not so limited, and it is intended that the following claims shall be construed broad enough to cover all equivalent structures so long as they are clear of the prior art. It is to be understood that the concept of manufacturing tubes having their clamping material 8| is fed across the guideway by any suitable means. The forming members 19 operate by swinging upwardly to engage and bend the clamps about the frame elements, as indicated at 8|. Similar forming members (not shown) will be used-above the frames to bend the top clamps down. At this time, bases l6, which may have the contact prongs already applied to them, are fed downwardly from a hopper 82 and dropped into position. These bases may also electrodes under tension is a broad concept which when coupled with the machine assembly herein shown and describedis not limited to the precise tube configuration disclosed. Consequently, the

x present disclosure is intended to be generic and to l. The method of assemblying electron dis- I charge tubes, which comprises passing a plurality of insulating elements in parallel spaced relation along a guideway, placing electrode elements between adjacent insulati elements during their travel through said guideway, placing contact elements between each electrode and one of the adjacent insulating elements, clamping the insulating elements together to place said electrodes under tension between them, and then cutting off the protruding portions of the electrode and contact elements, and sealing the assembly in an envelope.

2. The method of continuously assembling electron discharge tubes which comprises passing insulating elements along a passageway in spaced relation to one another and juxtaposed for subsequent assembly, feeding strip material along said passageway between said insulating elements, feeding contact material between each electrode and one of the adjacent insulating elements, clamping the insulating. elements and electrodes into closely engaging relation to bring the electrodes under permanent tension, cutting off the electrode material adjacent the face of the insulating elements, placing a base on the projecting contacts and cutting off the contacts,

and then sealing the assembly in an envelope.

3. The method of manufacturing electron discharge tubes which comprises feeding insulating spacing elements and electrodes in parallel relation through a passageway, clamping said assembled elements together, cutting off the excess material and then sealing the assembly in an envelope.

4., The method of continuous assembly of electron discharge tubes, which comprises feeding strip material for electrodes through a passage way with interspersed ring-like insulating elements, cutting off the electrode materials where they extend beyond the area subtended by the insulating elements, feeding terminal elements between each electrode and one of the insulating elements, clamping the insulating elements together to place the electrodes in contact with their terminals and placing the electrodes under tension, cutting off the terminals, attaching a base to said terminals, and then sealing the assembly in an envelope.

5. The method of continuously assembling an electron discharge tube, which comprises, feeding into a passageway parallel, spaced framelike insulating elements with interposed electrode material in continuous strips, clamping the stacked assembly of electrodes and insulating .elements together, and then cutting on the 10 discharge tube electrode unit including a plurality of electron tube-control electrodes which comprises continuously feeding a. plurality of parallel groups of parallel spaced wires from a con= tinuous source, feeding spacing elements between adjacent groups of wires and causing them to advance with the wire groups, securing all of the wires of each group with interposed spacing elements together at two longitudinally spaced points while said wires are maintained under tension, and then cutting off the wires so secured to sever them from the source and thus free a completed unit.

8. The method of manufacturing an electron discharge tube electrode unit including a plurality of electron tube control electrodes simultaneously which comprises feeding a plurality of groups of wires in parallel spaced relation from a continuous source, feeding spacing means between adjacent wire groups for maintaining each group in laterally spaced relation to each other group, advancing the spacing means with the wire groups, securing all of the wires of each group in the parallel spaced relation in which they are fed and at two longitudinally spaced points, and simultaneously securing all of the groups and spacing means together, and then severing the wires from the source to form a complete assembled unit.

. 9. The method of manufacturing an electron discharge tube unit including a plurality of electron tube control electrodes simultaneously which comprises feeding a plurality of groups of wires in parallel spaced relation from a continuous source, feeding spacing elements of insulation between adjacent wire groups for maintaining each wire group in laterally spaced relation to each other group, advancing'the spacing ele-.

ments with the wire groups, feeding conducting elements between the wire groups to form electrical connections between the wires of each Number Name Date 1,430,634 Fischer Oct. 3, 1922 1,456,506 Leveridge May 29, 1923 1,716,153 Rottgardt June 4,1929 2,141,655 Kott Dec. 27, 1939 2,141,654 Kott Dec. 2'7, 1938 2,145,727 Lloyd Jan. 31. 1939 2,217,427 Zinke Oct. 8, 1940 1,934,097 Simon Nov. 7, 1933 i FOREIGN-PATENTS Number Country Date group, clamping the wire groups, conducting elements and spacing elements together to form a unit, and then severing the wires from the source.

- FRANK H. McINTOSH.

REFERENCES orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS German Oct. 23, 1919 

